diff --git a/functions-common b/functions-common
index 52d80fb95b..ff9261161c 100644
--- a/functions-common
+++ b/functions-common
@@ -1629,7 +1629,6 @@ function disable_all_services {
 function disable_negated_services {
     local to_remove=""
     local remaining=""
-    local enabled=""
     local service
 
     # build up list of services that should be removed; i.e. they
@@ -1644,21 +1643,7 @@ function disable_negated_services {
 
     # go through the service list.  if this service appears in the "to
     # be removed" list, drop it
-    for service in ${remaining//,/ }; do
-        local remove
-        local add=1
-        for remove in ${to_remove//,/ }; do
-            if [[ ${remove} == ${service} ]]; then
-                add=0
-                break
-            fi
-        done
-        if [[ $add == 1 ]]; then
-            enabled="${enabled},$service"
-        fi
-    done
-
-    ENABLED_SERVICES=$(_cleanup_service_list "$enabled")
+    ENABLED_SERVICES=$(remove_disabled_services "$remaining" "$to_remove")
 }
 
 # disable_service() removes the services passed as argument to the
@@ -1762,6 +1747,30 @@ function is_service_enabled {
     return $enabled
 }
 
+# remove specified list from the input string
+# remove_disabled_services service-list remove-list
+function remove_disabled_services {
+    local service_list=$1
+    local remove_list=$2
+    local service
+    local enabled=""
+
+    for service in ${service_list//,/ }; do
+        local remove
+        local add=1
+        for remove in ${remove_list//,/ }; do
+            if [[ ${remove} == ${service} ]]; then
+                add=0
+                break
+            fi
+        done
+        if [[ $add == 1 ]]; then
+            enabled="${enabled},$service"
+        fi
+    done
+    _cleanup_service_list "$enabled"
+}
+
 # Toggle enable/disable_service for services that must run exclusive of each other
 #  $1 The name of a variable containing a space-separated list of services
 #  $2 The name of a variable in which to store the enabled service's name
diff --git a/lib/tempest b/lib/tempest
index 211ff357e1..5599684eef 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -91,10 +91,7 @@ function remove_disabled_extensions {
     local extensions_list=$1
     shift
     local disabled_exts=$*
-    for ext_to_remove in ${disabled_exts//,/ } ; do
-        extensions_list=${extensions_list/$ext_to_remove","}
-    done
-    echo $extensions_list
+    remove_disabled_services "$extensions_list" "$disabled_exts"
 }
 
 # configure_tempest() - Set config files, create data dirs, etc
diff --git a/tests/test_functions.sh b/tests/test_functions.sh
index 1d82792ca7..f555de8dff 100755
--- a/tests/test_functions.sh
+++ b/tests/test_functions.sh
@@ -137,6 +137,31 @@ test_disable_negated_services 'a,aa,-a' 'aa'
 test_disable_negated_services 'a,av2,-a,a' 'av2'
 test_disable_negated_services 'a,-a,av2' 'av2'
 
+echo "Testing remove_disabled_services()"
+
+function test_remove_disabled_services {
+    local service_list="$1"
+    local remove_list="$2"
+    local expected="$3"
+
+    results=$(remove_disabled_services "$service_list" "$remove_list")
+    if [ "$results" = "$expected" ]; then
+        passed "OK: '$service_list' - '$remove_list' -> '$results'"
+    else
+        failed "getting '$expected' from '$service_list' - '$remove_list' failed: '$results'"
+    fi
+}
+
+test_remove_disabled_services 'a,b,c' 'a,c' 'b'
+test_remove_disabled_services 'a,b,c' 'b' 'a,c'
+test_remove_disabled_services 'a,b,c,d' 'a,c d' 'b'
+test_remove_disabled_services 'a,b c,d' 'a d' 'b,c'
+test_remove_disabled_services 'a,b,c' 'a,b,c' ''
+test_remove_disabled_services 'a,b,c' 'd' 'a,b,c'
+test_remove_disabled_services 'a,b,c' '' 'a,b,c'
+test_remove_disabled_services '' 'a,b,c' ''
+test_remove_disabled_services '' '' ''
+
 echo "Testing is_package_installed()"
 
 if [[ -z "$os_PACKAGE" ]]; then